Determination of a High Potential Barrier Hindering Internal Rotation in 2-Methylcyclopentanone and α-Methyl-γ-Butyrolactone by Microwave Fourier Transform Spectroscopy

1992 ◽  
Vol 47 (6) ◽  
pp. 761-764 ◽  
Author(s):  
J. L. Alonso ◽  
N. Heineking ◽  
H. Dreizler ◽  
N. Heineking ◽  
H. Dreizler
Keyword(s):  
Fourier Transform ◽  
Internal Rotation ◽  
Excited States ◽  
Fourier Transform Spectroscopy ◽  
Vibrationally Excited ◽  
Methyl Group ◽  
Internal Rotation Barrier ◽  
High Potential Barrier ◽  
Method Analysis

AbstractThe microwave spectra of α-methyl-γ-butyrolactone and 2-methylcyclopentanone have been reinvestigated using microwave Fourier transform spectroscopy. A-E splittings due to internal rotation of the methyl group have been observed in the ground and several vibrationally excited states for both molecules. From an internal-axis-method analysis of these splittings, values of the methyl group internal rotation barrier of 2.61 kcal mol-1 for α-methyl-γ-butyrolactone and 2.41 kcal mol-1 for 2-methylcyclopentanone have been obtained.

High Resolution Microwave Spectroscopy of Ethyl Vinyl Ether: Accurate Determination of the Methyl Top Internal Rotation Barrier

2000 ◽  
Vol 55 (5) ◽  
pp. 481-485 ◽  
Author(s):  
H. Dreizler ◽  
N. Hansen
Keyword(s):  
Internal Rotation ◽  
Vinyl Ether ◽  
Accurate Determination ◽  
Ethyl Vinyl Ether ◽  
Ethyl Vinyl ◽  
Methyl Group ◽  
Rotational Spectra ◽  
Internal Rotation Barrier ◽  
In Trans

Abstract We have performed an investigation of the internal rotation of the methyl group in trans-cis ethyl vinyl ether by using molecular beam-Fourier transform Microwave (MB-FTMW) spectroscopy. Rotational spectra (up to J = 20) were recorded in the frequency region 4-19 GHz. Due to the internal rotation of the methyl group, some rotational transitions were split and the torsional barrier could be determined to V3 (CH3) = 1074.4(4) cm-1 .

The Microwave Spectra of m-Xylene and m-Xylene-d10. Determination of the Low Methyl Internal Rotation Barrier

2001 ◽  
Vol 56 (9-10) ◽  
pp. 635-640 ◽  
Author(s):  
C. Thomsen ◽  
H. Dreizler
Keyword(s):  
Fourier Transform ◽  
Internal Rotation ◽  
Microwave Spectroscopy ◽  
Methyl Groups ◽  
Rotation Barrier ◽  
Rotational Constants ◽  
Moments Of Inertia ◽  
Rotational Spectra ◽  
Internal Rotation Barrier

Abstract The rotational spectra of m-xylene, (CH3)2C6H4 and of m-xylene-d10, (CD3)2C6D4 have been recorded between 6 and 26.5 GHz using pulsed beam Fourier transform microwave spectroscopy. The clue for the assignment of the internal rotation multiplets was the inertial defect derived from the A1A1 species transitions. The rotational constants for m-xylene and m-xylene-d10 are A = 3572.1117(1) MHz / 2896.1195(17) MHz, B = 1761.8621(1) MHz / 1446.0236(15) MHz, C =1197.3943(2) MHz / 988.2357(7) MHz, the barrier to internal rotation of the two methyl groups are V3 = 53.7(16) J/mol / 39.8(5) J/mol, their moments of inertia were assumed to be I∞= 3.14 uÅ2 / 6.28 uÅ2.

Determination of a High Potential Barrier Hindering Internal Rotation from the Ground State Spectrum The Methylbarrier of cis-Propanal

1982 ◽  
Vol 37 (9) ◽  
pp. 1035-1037 ◽  
Author(s):  
J. A. Hardy ◽  
A. P. Cox ◽  
E. Fliege ◽  
H. Dreizler
Keyword(s):  
Internal Rotation ◽  
Potential Barrier ◽  
Ground State ◽  
Model Errors ◽  
Centrifugal Distortion ◽  
Methyl Group ◽  
Distortion Analysis ◽  
High Potential Barrier ◽  
Double Resonances

Abstract The barrier hindering internal rotation of the methyl group was determined by analysing the splittings of rotational lines in the ground state. So model errors are minimized. The assignment was checked by double resonances and a centrifugal distortion analysis.

scholarly journals Determination of a High Potential Barrier Hindering Internal Rotation from the Ground State Spectrum

1983 ◽  
Vol 38 (9) ◽  
pp. 1010-1014 ◽  
Author(s):  
W. Stahl ◽  
H. Dreizler ◽  
M. Hayashi
Keyword(s):  
Internal Rotation ◽  
Potential Barrier ◽  
Ground State ◽  
High Potential ◽  
Rotational Spectrum ◽  
High Potential Barrier

Abstract We present an analysis of the rotational spectrum of ethylchloride-35Cl in the ground state. The 35Cl-hfs analysis was extended and the barrier to internal rotation determined from narrow splittings of high J-transitions.

Determination of a High Barrier Hindering Internal Rotation from the Ground State Spectrum. The Methylbarrier of Propane

1985 ◽  
Vol 40 (3) ◽  
pp. 271-273 ◽  
Author(s):  
G. Bestmann ◽  
W. Lalowski ◽  
H. Dreizler
Keyword(s):  
Fine Structure ◽  
Internal Rotation ◽  
Ground State ◽  
Methyl Groups ◽  
Rotational Spectrum ◽  
Rotation Barrier ◽  
Rotation Axes ◽  
Internal Rotation Barrier ◽  
The Moment

The internal rotation barrier V3, the moment of inertia Iα of the methyl tops and the angle between the two internal rotation axes were determined from the torsional fine structure of the rotational spectrum in the torsional ground state. A tilt angle of 1.4° of the methyl groups toward each other results.

scholarly journals Internal Rotation Analysis of the Ground State Microwave Spectrum of 2-Bromopropene

1984 ◽  
Vol 39 (7) ◽  
pp. 637-645
Author(s):  
E. Fliege ◽  
H. Dreizler
Keyword(s):  
Fourier Transform ◽  
Internal Rotation ◽  
Ground State ◽  
Fourier Transform Spectroscopy ◽  
Microwave Spectrum ◽  
Isotopic Species ◽  
Quadrupole Coupling ◽  
Methyl Rotation

The microwave spectrum of 2-bromopropene was reinvestigated with the use of microwave Fourier transform spectroscopy. For the two isotopic species CH3C79Br=CH2 and CH3C81Br=CH2 the bromine quadrupole coupling was determined with higher accuracy. The barrier hindering internal methyl rotation was obtained from the ground state.

Determination of a High Potential Barrier Hindering Internal Rotation from the Ground State Spectrum. The Methylbarrier of Ethylbromide

1985 ◽  
Vol 40 (6) ◽  
pp. 575-587 ◽  
Author(s):  
J. Gripp ◽  
H. Dreizler ◽  
R. Schwarz
Keyword(s):  
Hyperfine Structure ◽  
Internal Rotation ◽  
Potential Barrier ◽  
Ground State ◽  
Rotational Spectrum ◽  
Centrifugal Distortion ◽  
Vibrational Ground State ◽  
Distortion Analysis ◽  
High Potential Barrier

For ethylbromide a determination of the parameters of internal rotation is given derived from the rotational spectrum of the torsional and vibrational ground state. The Br-hyperfine structure is reanalysed with higher precision. As high J transitions were measured a centrifugal distortion analysis was necessary.

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